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Impact of zero order unconverted light on beam pointing

Description: There is a significant amount of unconverted light incident in the NIF target chamber. The baseline plan for managing this light is to use a sub-aperture CSG design. This CSG selection impacts the target chamber and near-opposing FOAs due to: (1) zero order unconverted light footprint, and (2) high order dispersed unconverted light. In this memo we describe the impact of the zero order light on the range of beam pointing for individual beams. We show that zero order footprint for 1w light enters into the near-opposite FOAs for several ports if the beams are pointed away from the target chamber center. Additionally, for the case where 3w is allowed to propagate past target chamber center, the converted light may enter into the near-opposite FOAs. The second aperture in the PAM is required to protect the FOAs and still accommodate offset beam pointing on NIF. We present details on the aperture requirements to accommodate a range of beam pointing.
Date: August 24, 1999
Creator: Dixit, S; Kalantar, D & Lyons, R
Partner: UNT Libraries Government Documents Department

Progress in the development of superconducting quadrupoles for heavy ion fusion

Description: The Heavy Ion Fusion program is developing single aperture superconducting quadrupoles based on NbTi conductor, for use in the High Current Experiment at Lawrence Berkeley National Laboratory. Following the fabrication and testing of prototypes using two different approaches, a baseline design has been selected and further optimized. A prototype cryostat for a quadrupole doublet, with features to accommodate induction acceleration modules, is being fabricated. The single aperture magnet was derived from a conceptual design of a quadrupole array magnet for multi-beam transport. Progress on the development of superconducting quadrupole arrays for future experiments is also reported.
Date: May 24, 2002
Creator: Faltens, A.; Lietzke, A.; Sabbi, G.; Seidl, P.; Lund, S.; Manahan, B. et al.
Partner: UNT Libraries Government Documents Department

INTERACTION REGION MAGNETS FOR VLHC.

Description: The interaction region (IR) magnets for the proposed very large hadron collider (VLHC) require high gradient quadrupoles and high field dipoles for high luminosity performance. Moreover, the IR magnets for high energy colliders and storage rings must operate in an environment where the amount of energy deposited on superconducting coils is rather large. In the case of doublet IR optics with flat beams, the design of the first 2-in-1 quadrupole defines the geometry and pole tip field in this and other IR magnets. This paper will present a novel design of this magnet that allows a very small separation between the two apertures. A brief discussion of the conceptual magnetic design of this and other magnets for interaction regions is given. The influence of critical current density in superconductor (a higher value of which is most beneficial to high performance IR magnet design) is also discussed. Since High Temperature Superconductors (HTS) retain most of their critical current density at high fields and at elevated temperatures, they offer an attractive possibility for the IR magnet designs of future colliders or upgrades of present colliders.
Date: September 24, 2001
Creator: Gupta, R. & Harrison, M.
Partner: UNT Libraries Government Documents Department

Modified Visible and Infrared Optical Design for the ITER Upper Ports

Description: This document reports the results of a follow-on optical design study of visible-light and infrared optics for the ITER upper ports, performed by LLNL under contract for the US ITER Project Office. The major objectives of this work are to move the viewing aperture closer to the plasma so that the optical path does not cut through any adjacent blanket shield module other than the module designated for the port; move optics forward into the port tube to increase the aperture size and therefore improve the spatial resolution; assess the trade-off between spatial resolution and spatial coverage by reducing the field of view; and create a mechanical model with a neutron labyrinth. Here we show an optical design incorporating all these aspects. The new design fits into a 360 mm ID tube, as did the previous design. The entrance aperture is increased from 10 mm to 21 mm, with a corresponding increase in spatial resolution. The Airy disk diameter for 3.8 {micro}m wavelength IR light is 5.1 mm at the most distant target point in the field of view. The field of view is reduced from 60 toroidal degrees (full toroidal coverage with 6 cameras) to 50 toroidal degrees. The 10 degrees eliminated are those nearest the camera, which have the poorest view of the divertor plate and in fact saw little of the plate. The Cassegrain telescope that was outside the vacuum windows in the previous design is now in vacuum, along with lenses for visible light. The Cassegrain for visible light is eliminated. An additional set of optical relay lenses is added for the visible and for the IR.
Date: April 24, 2008
Creator: Lasnier, C; Seppala, L & Morris, K
Partner: UNT Libraries Government Documents Department

Space-Charge Effects in the Gas Detector

Description: Discussion of space-charge effects in a photoluminescence cell that will be used as a non-disruptive total energy monitor at the LCLS facility is presented. Regimes where primary photoelectrons will be confined within the X-ray beam aperture are identified. Effects of the space-charge on the further evolution of the electron and ion populations are discussed. Parameters of the afterglow plasma are evaluated. Conditions under which the detector output will be proportional to the pulse energy are defined.
Date: September 24, 2007
Creator: Ryutov, D; Hau-Riege, S & Bionta, R
Partner: UNT Libraries Government Documents Department

Fast Pulsing Neutron Generators for Security Application

Description: Active neutron interrogation has been demonstrated to be an effective method of detecting shielded fissile material. A fast fall-time/fast pulsing neutron generator is needed primarily for differential die-away technique (DDA) interrogation systems. A compact neutron generator, currently being developed in Lawrence Berkeley National Laboratory, employs an array of 0.6-mm-dia apertures (instead of one 6-mm-dia aperture) such that gating the beamlets can be done with low voltage and a small gap to achieve sub-microsecond ion beam fall time and low background neutrons. Arrays of 16 apertures (4x4) and 100 apertures (10x10) have been designed and fabricated for a beam extraction experiment. The preliminary results showed that, using a gating voltage of 1200 V and a gap distance of 1 mm, the fall time of extracted ion beam pulses is approximately 0.15 mu s at beam energies of 1000 eV.
Date: April 24, 2009
Creator: Ji, Q.; Regis, M. & Kwan, J. W.
Partner: UNT Libraries Government Documents Department

Multi-objective direct optimization of dynamic acceptance and lifetime for potential upgrades of the Advanced Photon Source.

Description: The Advanced Photon Source (APS) is a 7 GeV storage ring light source that has been in operation for well over a decade. In the near future, the ring may be upgraded, including changes to the lattice such as provision of several long straight sections (LSS). Because APS beamlines are nearly fully built out, we have limited freedom to place LSSs in a symmetric fashion. Arbitrarily-placed LSSs will drastically reduce the symmetry of the optics and would typically be considered unworkable. We apply a recently-developed multi-objective direct optimization technique that relies on particle tracking to compute the dynamic aperture and Touschek lifetime. We show that this technique is able to tune sextupole strengths and select the working point in such a way as to recover the dynamic and momentum acceptances. We also show the results of experimental tests of lattices developed using these techniques.
Date: August 24, 2010
Creator: Borland, M.; Sajaev, V.; Emery, L.; Xiao, A. & (APS), Accelerator Systems Division
Partner: UNT Libraries Government Documents Department

The effect of the light round-trip time on the performance of an adaptive optics turbulence compensation system

Description: The propagation of a laser beam through atmospheric turbulence can, under many circumstances, be compensated to near diffraction limited levels, by use of an adaptive optics system. In the ideal case, a beacon light source is generated at the aimpoint. This light traverses through the turbulent path back to the aperture. The distribution of phase perturbations in the aperture plane is sensed, and the reverse of this phase is applied to the outgoing beam. When the turbulent path is long (i.e. a few hundred kilometers), and the effective wind speed is high (such as in the case when the laser is based on a plane, with airspeeds around 200 m/s), the performance of the adaptive optics system can be significantly degraded due to the time delay from when the beacon samples the turbulence, until the beam propagates through the turbulence. This effect has not been treated in the past, because for astronomical applications, the time delays due to the round trip of light are too short (tens of microseconds) to cause problems. This paper presents an analysis of the anisoplanatic effect of the round trip time of light. A formulation of the phase variance has been constructed for this effect. The time response of the adaptive optics system (i.e. servo bandwidth) is intimately related to the light round trip time effect, and is included in the analysis. Results are first obtained for the large aperture limit, and then the effects of finite aperture size are treated. A set of scaling relationships have been found that enable the formulation to be cast in a form that is insensitive to the turbulence strength profile along the propagation path.
Date: February 24, 1992
Creator: Stroud, P.
Partner: UNT Libraries Government Documents Department

High electric fields in a superconducting RFQ structure

Description: High surface electric fields have been obtained in the first tests of a superconducting rf quadrupole device. The rf quadrupole fields were generated between niobium vanes 6.5 cm in length, with an edge radius of 2 mm, and with a beam aperture of 6 mm diameter. In tests at 4.2 K, the 64 MHz device operated cw at peak surface electric fields of 128 MV/m. Virtually no electron loading was observed at fields below 100 MV/m. It was possible to operate at surface fields of 210 MV/m in pulses of 1 msec duration using a 2.5 kW rf source. For the vane geometry tested, more than 10 square centimeters of surface support a field greater than 90% of the peak field. The present result indicates that electric fields greater than 100 MV/m can be obtained over an appreciable area, sufficient for some accelerator applications. It also shows that superconducting rf technology may provide an extended range of options for rf quadrupole design. 7 refs., 4 figs.
Date: September 24, 1990
Creator: Delayen, J.R. & Shepard, K.W.
Partner: UNT Libraries Government Documents Department

The effect of the light round-trip time on the performance of an adaptive optics turbulence compensation system. Final report

Description: The propagation of a laser beam through atmospheric turbulence can, under many circumstances, be compensated to near diffraction limited levels, by use of an adaptive optics system. In the ideal case, a beacon light source is generated at the aimpoint. This light traverses through the turbulent path back to the aperture. The distribution of phase perturbations in the aperture plane is sensed, and the reverse of this phase is applied to the outgoing beam. When the turbulent path is long (i.e. a few hundred kilometers), and the effective wind speed is high (such as in the case when the laser is based on a plane, with airspeeds around 200 m/s), the performance of the adaptive optics system can be significantly degraded due to the time delay from when the beacon samples the turbulence, until the beam propagates through the turbulence. This effect has not been treated in the past, because for astronomical applications, the time delays due to the round trip of light are too short (tens of microseconds) to cause problems. This paper presents an analysis of the anisoplanatic effect of the round trip time of light. A formulation of the phase variance has been constructed for this effect. The time response of the adaptive optics system (i.e. servo bandwidth) is intimately related to the light round trip time effect, and is included in the analysis. Results are first obtained for the large aperture limit, and then the effects of finite aperture size are treated. A set of scaling relationships have been found that enable the formulation to be cast in a form that is insensitive to the turbulence strength profile along the propagation path.
Date: February 24, 1992
Creator: Stroud, P.
Partner: UNT Libraries Government Documents Department

Improved Optical Design for the Large Synoptic Survey Telescope (LSST)

Description: This paper presents an improved optical design for the LSST, an fll.25 three-mirror telescope covering 3.0 degrees full field angle, with 6.9 m effective aperture diameter. The telescope operates at five wavelength bands spanning 386.5 nm to 1040 nm (B, V, R, I and Z). For all bands, 80% of the polychromatic diffracted energy is collected within 0.20 arc-seconds diameter. The reflective telescope uses an 8.4 m f/1.06 concave primary, a 3.4 m convex secondary and a 5.2 m concave tertiary in a Paul geometry. The system length is 9.2 m. A refractive corrector near the detector uses three fused silica lenses, rather than the two lenses of previous designs. Earlier designs required that one element be a vacuum barrier, but now the detector sits in an inert gas at ambient pressure. The last lens is the gas barrier. Small adjustments lead to optimal correction at each band. The filters have different axial thicknesses. The primary and tertiary mirrors are repositioned for each wavelength band. The new optical design incorporates features to simplify manufacturing. They include a flat detector, a far less aspheric convex secondary (10 {micro}m from best fit sphere) and reduced aspheric departures on the lenses and tertiary mirror. Five aspheric surfaces, on all three mirrors and on two lenses, are used. The primary is nearly parabolic. The telescope is fully baffled so that no specularly reflected light from any field angle, inside or outside of the full field angle of 3.0 degrees, can reach the detector.
Date: September 24, 2002
Creator: Seppala, L
Partner: UNT Libraries Government Documents Department

High NA Nicrostepper Final Optical Design Report

Description: The development of a new EUV high NA small-field exposure tool has been proposed for obtaining mask defect printability data in a timeframe several years before beta-tools are available. The imaging system for this new Micro-Exposure Tool (MET), would have a numerical aperture (NA) of about 0.3, similar to the NA for a beta-tool, but substantially larger than the 0.10 NA for the Engineering Test Stand (ETS) and 0.088 NA for the existing 10x Microstepper. This memorandum discusses the development and summarizes the performance of the camera for the MET and includes a listing of the design prescription, detailed analysis of the distortion, and analysis demonstrating the capability to resolution 30 nm features under the conditions of partially coherent illumination.
Date: September 24, 1999
Creator: Hudyma, R
Partner: UNT Libraries Government Documents Department